Stir together sugar and cinnamon. Halve each grapefruit using a paring knife. Cut around the edgeof the grapefruit and between segments. Put on a cookie sheet. Sprinkle with sugar mixture. Place under broiler for about 5 minutes until golden and bubbly. WATCH CLOSELY!!
I have a little torch I use for this...the same as I use on my Creme Brulee!!Not my pic but looks exactly like this!!